Three wire circuit adapter



E. E. JOHNSON 2,802,192

THREE WIRE CIRCUIT ADAPTER Filed April 16, 1956 In Ve nior' I, Eww JvoHMSo/v United States Patent O THREE* WIRE CIRCUIT ADAPTER i Ewald E. Johnson, Wasco, Iii.

Application April 16, 1956, Serial No. 578,298 1 Claim. (Cl. 339-166) The invention relates to improvements in electric plug adapters and is more particularly concerned with the novel construction of yan adapter for reversing the polarity of electrical -current owing in a three wire circuit from a Source outlet receptacle to a three phase motor or like appliance.

It frequently happens that a three phase motor having a three wire conduit provided with a three pronged service plug has the plug so connected that when it is inserted into a source outlet receptacle, the polarity of the current owing to the motor causes it to operate in a direction reverse to that intended or required. The relationship of the service plug to the source outlet receptacle cannot be varied because the plug has its connector prongs especially arranged to be received in complementally arranged recesses in the source outlet receptacle in a predetermined manner. Considerable time is consumed in changing the wire connections to the plug or in changing the wiring leading from the current source to the source outlet receptacle.

Use of the present adapter avoids this inconvenient and time -consuming practice. The adapter consists generally of an insulating housing having three conductor prongs extending from one end for insertion into the source outlet receptacle recess and these prongs are electrically connected, Within the housing, to electric contact sockets provided in and opening onto the other end of the housing in such a manner that when the prongs on the service plug are inserted into said sockets the current phase is reversed and motor operation in the desired direction is obtained. It is, therefore, an object of the invention to provide a novelly constructed electric plug adapter.

Another object of the invention is to provide an electric plug adapter with conductor prongs Iand prong connector sockets wired in a manner to reverse the polarity of electric current flowing therethrough.

A further object of the invention is to provide an adapter plug that is easily and quickly connected in a three Wire circuit and which is not expensive to manufacture, is foolproof and safe to use, and is very rugged.

With the foregoing and such other objects in View which will appear `as the description proceeds, the invention consists of certain novel features of construction, arrangement and combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claim, it being understood that various changes in form, proportion, size and minor details of the structure may be made without departing from the spirit of the invention.

Referring to the drawings in which the same characters of reference are employed to identify corresponding parts:

Figure 1 is a longitudinal sectional view of an adapter embodying the features of the present invention;

Figure 2 is a top plan view of the adapter, as viewed along line 2-2 of Figure 1;

Figure 3 is a bottom plan view of the adapter, as viewed along line 3 3 of Figure 1; and,

Figure 4 is a three wire circuit diagram illustrating use of the adapter.

The adapter of the present invention includes an insulating body having three connector prongs projecting from one end for insertion into the three terminal sockets of a source outlet receptacle of a three wire circuit. The other end of the body carries three spring contacts which are arranged in substantial alignment with the prongs. An insulating cap is superimposed upon the base to conceal the spring contacts. The cap is preferably in the form of an inverted cup and it has three openings in its end wall, one in alignment with each spring contact, so as to admit into electrical contact with the spring contacts the three prongs on a conventional plug carried on the end of a three wire conduit leading to a three phase motor or other electrical appliance.

Referring now to the -accompanying drawings which illustrate an exemplary embodiment of the invention, the adapter includes an insulating body 11 in the form of a relatively thick disc suitably recessed circumferentiaily at one end, as at 12, to receive snugly the circumferential edge of a cap 13 which is formed substantially like an inverted cup and includes a circumferential wall 14 and top wall 15. An axial boss or hub 16 depends from the top wall 15 and seats against the top surface of the body so as `to provide reinforcement means. The boss 16 is centrally bored to receive the mounting screw 17 that extends through ya portion of the body and is engaged at its free depending end with a nut 18 for securing the cap firmly onto the body.

The other body end has a shallow circular recess 19 defining a surrounding flange 21 and said end is further recessed axially by the provision of a relatively deep cylindrical well 22. The circular recess 19 affords a mounting surface upon which are mounted three connector prongs 23, 24 and 25, each having a base or terminal connecting portion 26 carrying a wire connecting screw 27.

Mounted on the other body end, within the cap 13, are three electric contact elements preferably in the form of spring sockets 28, 29 and 30. These sockets may be secured to the body in any conventional manner and they are arranged one in substantial alignment with each of the prongs 23, 24 and 25 and each is in alignment with an opening in the cap end wall 15. These openings, identified as 28a, 29a and 30a provide means for insertion of the prongs of a service plug. As is perhaps best illustrated in Figure 4, an electric conductor 31 connects the prong 23 with the spring socket 28 in alignment therewith. Another electric conductor 32 connects the prong 24 with the spring socket 30 whereas an electric conductor 33 connects the prong 25 with the spring socket 29. The electric conductors extend through the axial recess 22 and through passageways 34 provided therefor in the body 11 and each is insulated from the other.

Referring now to Figure 4 in particular, it should be quite evident that the crossing of the conductors 32 and 33 carries the current in the supply wire 35 to the armature con 36 and the current in supply line 37 to the armature -coil 3S. Current from supply line 3'9 is delivered to armature coil 40 through conductor 31. This current ilow differs from that which would be obtained were the service plug S connected directly with the source outlet receptacle R, consequently the insertion of the adapter in the three wire circuit results in changing the direction of armature rotation without requiring any change in the conventional wiring.

Although an exemplary embodiment o-f the invention has been shown and described it should be understood that the invention is capable of being embodied in a wide variety of modified structures and that it is not desired to limit the invention to the disclosure but to embrace suchf variations as wil-irfall'within the scope of the appended claim.

I claim as my invention:

An electric plug adapter for connecting a service plug to. ai source .outlet receptacletin; anthree-vwireY `circuiti comprising, an insulating housing including a relativelythicln circular body havingan. annular. shouldertoneoneendiand an inverted, cup-shapedrcap tted over;r saidshoulder, with. its endwall spacedffromfthe body, meanslsecuring.- the` cap. on said. body, three `conductor prongslmounted: on theother body end andextending. outwardly therefrom for engagementwith electric contacts of aA source outlet receptacle, terminal connectors. one Von the. mountedzend ofieach prong, an axial `recessin the last namedlbodyiend,

passageways connecting. said recessr with .the AinteriorA of the cap, three: apertures in the cap y.endWalL one inralign-H ment with each conductorprong, spring contact elements. mounted on the capped lbody endlwithin the capandone inv register with each aperture, each to.receivein elec- -trical connection therewith a prong. onia service. plug,

5 with a non-aligned contact element, and a third electrical conductor connecting the terminal connector of the remaining conductor prong with the remaining contact element, said conductors being threaded one through each passageway and being insulated one from the other.

References Cited in the le of this patent UNITED STATES PATENTS 1,489,283 Smyth Apr. 8, 1924 5 2,448,452 Morelock Aug. 3l, 1948 2,531,719 Alvino Nov. 28, 1950 FOREIGN PATENTS 324,007 Great Britain Jan. 13, 1930 971,318V France July 5, 1950 

